Yes Gumvbo, I want to retain EFI system, as I will retain the LPG sytem, so I need an intake manifold that support 8 injectors.(other 8 LPG are not difficult to install)
I'm searching it and I think that it is real possible to find but if I'm wrong I will modified an existing intake manifold with correct flow for the combo.
Waiting for suggestion by experts!!
Thanks

lollo, I am not sure your existing injection system is a direct bolt-on onto a pre-vortec manifold, independently of the LPG.
Let's see if we get some answers to this question.

As far as Multiport LPG injection goes, I have heard of the 8 injectors all "crowned" around the throttle body, in order to fit a Sequential Multiport LPG system onto a TBI motor.
That might be an option in case you need to switch to a TBI.
But you will need to make a research on the subject with the help of a specialist.

Hooker also makies the 2806 hkr SUPER COMPETITION series with 1 3/4" primaries and 3" collectors with longer equal length primaries painted black
2806 1hkr are ceramic coated
The super comps are about twice the cost of the Comps. All teh Hooker headers will require you to weld in the EGR bung that feeds teh EGR system loctaed on teh drivers side exhaust manifold. There is a hose that runs from the drivers manifold to the drivers sside front of the intake manifold.

Here is the stock CSFI spider above the GM retrofit MPFI replacement spider. Both flow the same 23.4 lb/hr at 63psi of fuel pressure the stock regulators are set at.

Ramjet 350 intake, works with Vortec heads

This is teh Mercruiser marine intake manifold that I use on my reg can shortbox Vortec 350 truck MArineintake left, stock CSFIO intake right

LPG has a 102-108 RON octane ratings
Stoich for propane is 15,67:1 by mass, and natural gas is 17.2:1 by mass.

I am knowledgeable about the CSFI Vortec L31 96-99 GMT400 truck systems. I laso calibrate my own PCM's(computers) for these as well, so ask away. Others here like those who have been helping you can build a better engine than I can.

The magnaflow dual cats are replacement for stock or shorty headers, maybe for tri-y.
If I will use magnaflow dual cats and long tube headers 1 5/8 I need to modified the pipes.
If I will do it, may I use an X or H equalizer before the cats or after the cats?

hahahaha I've start the thread for camshaft and now we are talking about all the combo parts.........great!!!!

That intake will work, but your stock intake will work as well.
If you are going to use a differnt intake manifold and wire in the injectors, here is a schematic, the pink wires are switched grounds. These coloured wires match the GM colur codes for the wires that you will find on teh stock injector wire harness on your truck.

A set of shorty headers will bolt directly to the Magnaflow dual cat replacement. Mid lengths would require cutting and welding, as would longtube headers.

the problem about h or X pipes on these Vortec vehicles is that it is almost impossible to get the amount of pipe in front of the x or H pipe exactly the same on both sides. This is because of the way that the stock fuel tank forces all of the exhaust over to the passenger side of the truck.

This is the cat forwqard exhaust fromMagnaflow for a 3/4 ton truck.

And the back section

Same parts but from Walker

Walker back section

As you can see the pipes and cats are larger for more flow. MAybe not needed, but just wanted to show you.

It should be noted that SOME Tahoes used exhaust that had the stock cats on the passenger and drivers side of the vehicle. The fuel tank isnt up front and in the way like in the trucks. Maybe you can run your exhaust straightback?

Thank you Hog!
The intake manifold and injectors will be different because the head are not vortec as OEM.
I will use EQ heads 76cc !
What I'm looking for is an intake manifold for pre-vortec heads that support 8 EFI injectors.

Thank you Hog!
The intake manifold and injectors will be different because the head are not vortec as OEM.
I will use EQ heads 76cc !
What I'm looking for is an intake manifold for pre-vortec heads that support 8 EFI injectors.

Gotcha, you could look into a TPI setup then, if youa re after mid rpm torque, its tough to beat the good old TPI intakes. And they look good too.

Hi Hog,
I need to find something that fit The EQ heads and is from idle to 5000 rpm.
The engine will be an high low end torque.
The truck is lifted 3 inch body, so I have more cleareance to the hood.
Thanks a lot!

That is a simulation that did indeed use a 500cfm TPI setup.
TPI setups use helmholtz resonance tuning to literally cram air into the heads at a specific rpm.
The stock TPI intakes were noted for their mid rpm torque and lack of upper rpm breathing compared to other intake manifolds.
Stock L98's were rated at 250hp@400rpm/340lb/ft@3200rpm.
IMO I dont think that there would be a better PFI intake manifold for this engine.
Unless you went with a TBI induction. The TBI L05 350 in the 95 1/2 ton truck which were rated at 210hp@3600rpm/300lb/ft@2800rpm or 190hp@4000/rpm/300lb/ft@2400rpm.
But I wouldnt suggest a TBI setup over a TPI setup.

Hi Hog, thank you, your TPI intake looks great!
I don't Know which kind of intake have used Techinspector1 in the simulation. I have to ask him.
I,ve wrote to Rogers performance, that sells me the EQ Heads, and he suggest me the XT pro-flow Edelbrock.

Hi Hog, thank you, your TPI intake looks great!
I don't Know which kind of intake have used Techinspector1 in the simulation. I have to ask him.
I,ve wrote to Rogers performance, that sells me the EQ Heads, and he suggest me the XT pro-flow Edelbrock.

If you look at page #1 on TechInspectors post, it literally says "500 cubic feet per minute TPI intake manifold was used"

Here is a copy of said passage with the TPI part highlighted:
This Sim was run with a 500 CFM Tuned Port Injection setup and 1 5/8" long tube headers through mufflers. Suggest installation of "X" or "H" pipe before the mufflers to smooth exhaust note and increase fuel mileage slightly.

The intake you have shown is a great intake, it woudl be suited for higher rpms though, far higher than a 2000rpm torque peak.
That intake is available as part of a complete kit that includes and ECM to control it. Not sure if it would control an electronic transmission though.
But its a nice setup for sure.

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